<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>基本选择器</title>
</head>
<body>
<div id="div1">div1</div>
<div class="cls">div2</div>
<div class="cls">div3</div>

</body>
<script src="js/jquery-3.3.1.min.js"></script>
<script>
    //1.id选择器
    let div1=$("#div1");
    //alert(div1.length);

    //2.元素选择器
    let divs=$("div");
    //alert(divs.length);

    //3.类选择器
    let cls=$(".cls");
    alert(cls.length);
</script>
</html>